I geared mine down to 13/39. I ride steep rocky trails, and that gearing is excellent. If you have wide open spaces to ride in, it's probably too low. But for tight woods, and rock climbing, I think it's the way to go. I spend alot less time searching for that perfect gear. Previously, I was shifting back and forth between first and second. It always seemed to be either too low or to high. I was also using first gear way more than I would like to. The new setup makes 2nd and third gears very usable. Sprocket Specialists has the sprockets, I've ordered a few from there, all with good luck. I have a 40 tooth brand new one, if anyone is interested.
Scott